The present invention will be described in connection with its preferred use, and that is to guide a biopsy needle during its insertion into human tissue to reach a lesion such as in a breast. The invention is not limited to this one use as it may be used in other instances, e.g., the X-ray of a fractured bone and provision of a locating and guiding beam to guide the proper angularity of a screw being threaded into the bone at a precise location and angle to secure bone fragments or a prothesis in a proper position.
In recent years the public has become very aware of the importance of X-ray examination of women's breasts in the control and cure of breast cancer. The early detection of cancerous tumors is recognized as significantly improving the chances of successful treatment. As a consequence, women of a certain age or genealogical background are subject to X-ray examination of their breasts at frequent intervals. Such examination often detects tumors or lesions which are of a questionable character, it being impossible to determine from the X-ray whether the tumor or lesion is malignant or benign. In such situations, it is normal to take a specimen or biopsy of the tumor or lesion to permit a careful examination of the abnormal tissue.
The most common means of taking a biopsy of a tumor or lesion in a woman's breast is a stereostatic device which uses an elongated needle which may be inserted with a rotary movement to cut a core sample of tissue in the area of the tumor or lesion. The needle is equipped with suction means to aid in extracting the cylindrical section of tissue. Since the current trend is toward early detection through frequent examination, the tumor or lesion which is to be checked through the biopsy is often very small and barely discernable on the X-ray. With the tumor or lesion often being well below the skin surface, it is extremely difficult to insert the biopsy needle with sufficient accuracy to engage and sample the area of tissue that is of interest and requires further testing.
In the presently used procedure, the breast of the patient is compressed against a horizontal surface below which the X-ray film is positioned. The compressing member is placed above the breast, clamping it against the surface, leaving a panel of skin exposed through a rectangular opening which has indicia on the sides of the opening to aid in establishing the location of the tumor discovered on the X-ray. By establishing the coordinates of the location of the tumor from the X-ray, a mark is placed on the location on the exposed skin using the indicia beside the opening to show where the biopsy needle should be inserted. An additional X-ray is taken to show the depth of the tumor so that the needle may be inserted and the specimen taken at the proper depth below the skin surface. After a biopsy specimen has been taken, another X-ray is taken to assure that the biopsy specimen is from the suspected tissue.
Because of the limited size of the tissue to be sampled and the possible errors in correlating the location of the needle insertion with the location of the tumor as shown on the X-ray, it is not unusual for many needle insertions to be required before achieving the proper location of the needle with respect to the tumor. The procedure causes considerable pain and discomfort and the prolongation resulting from the techniques employed suggest that improved techniques are required.
One attempt at locating the biopsy needle more precisely with respect to an X-ray picture of a tumor has involved the use of movable cross wires to create a shadow produced by an incandescent lamp to locate the needle insertion point on the skin. This technique has not proven to be particularly helpful, since the shadow image of the wires was not sharp enough to give a precise location and the normal ambient light in the area was usually too high to permit good visibility of the shadow image of the wires.
Another approach involved use of a laser dot which was projected in from the side to spot the needle insertion location on the skin. The angle at which the laser beam was projected tended to introduce errors since any deflection of the skin would cause the laser spot to shift location.
Another problem associated with biopsy is the difficulty of inserting and guiding the needle at the correct angle so that the needle tip is not displaced to a side of the tumor when the needle is inserted to the proper depth. The coordinates of the position of the tumor are determined from an X-ray beam that is usually located twenty inches or so above the X-ray film located beneath the breast. Herein, the X-ray beam emanates from an X-ray source that may be considered a point source because the X-ray beam that expands in size as it travels to X-ray film. At one particular location, e.g., usually at a coordinate designated D-5, the X-ray beam is directly vertical over the coordinate and the beam is perpendicular to the underlying X-ray film. A tumor located at D-5 will be hit by a needle located at the D-5 coordinate and guided perpendicular to the film and along a true vertical line. In such a system, when a breast tumor is located at the rear corners of the opening in the paddle, the X-ray beam from the point source may be at an angle of 3.degree. to 5.degree. with respect to the vertical. If the needle tip is inserted only along a true vertical plane, there is a chance that the needle tip may be displaced at an angle from the tumor missing the tumor, and this may necessitate the taking of another sample. Needless to say, such misses can be painful; and the uncomfortable position of the patient may be needed to be maintained considerably longer than necessary if the angle of needle insertion had been the same as the angle of X-ray beam. The lesions can be very small so that the missing of the lesion can occur quite easily.
In the aforesaid patent application, a continuous mark in the form of a cross or cross hair was generated from a unit located about six inches away from the X-ray point source. While the instrument disclosed in this application was a vast improvement over the conventional equipment, and has been used satisfactorily, the present invention is directed to the elimination of parallax that might be present in such devices. That is, the present invention eliminates the difference in apparent direction of the tumor, as seen from the X-ray point source on the one hand, and the laser source for the cross hair mark on the other hand. More specifically, the laser source is moved to eliminate parallax and to guide the needle along the angle and to the position of the tumor to assure that the needle is inserted at the same angle as the X-ray beam from the X-ray point source. Thus, when a second X-ray is taken, it should verify that the biopsy sample is taken from the tumor previously located for sampling.